<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>闭包的弊端</title>
</head>
<body>
    <script type="text/javascript">
        function fn1() {
          var a = 2;
      
          function fn2() {
            a++;
            console.log(a);
          }
      
          return fn2;
        }
        var f = fn1();
      
        f(); // 3
        f(); // 4
      
        f = null // 释放
      </script>
</body>
</html>